Metal alloy and use thereof

ABSTRACT

A metallic alloy comprising Ti, Zr, Nb, containing an amorphous phase and a quasicrystalline phase and is represented by the formula: 
       Ti a Zr b Nb c M d I e , 
     wherein:
         M represents an element selected from a group consisting of Ni, Co, Fe, Mn,   I represents impurities,   coefficients a, b, c, d, e represent atomic %, and are equal to: 40≦a≦55, 5≦b≦30, 5≦c≦25, 5≦d≦30, e≦1.

BACKGROUND

The object of the invention is a metal alloy, useful in particular as abiomaterial.

Biomaterials must imperatively obey to specific criteria regarding thephysical, chemical and mechanical properties, such as mechanicaldurability, chemical inertness, resistance to corrosion, bio-adhesion.

Titanium alloys have demonstrated superior biocompatibility amongcandidate metallic biomaterials however this class of alloys exhibitsinferior tribological properties than those of for example Cr—Co—Moalloys.

The mechanical properties and biocompatibility of titanium alloys can beimproved by forming them as metallic glass having amorphous ornanocrystalline structure. Recent progresses in the field of researchhas demonstrated that amorphous and quasicrystalline phases can beprepared for several compositions based on combinations of titanium,zirconium and metals such as palladium, cobalt, nickel, copper:Ti—Zr—(Ni,Co,Pd), Ti—Zr—(Ni,Pd), Ti—Zr—(Ni,Co) and Ti—Zr—Co. However,these metallic glasses did not comply with all requirements ofbiocompatibility. Moreover, palladium is an expensive material. Anexemplary metallic glass of this type is Ti₄₀Zr₁₀Cu₃₆Pd₁₄ described inpublications: Fengxiang Qin, Masahiro Yoshimura, Xinming Wang, ShengliZhu, Asahi Kawashima, Katsuhiko Asami i Akihisa Inoue “CorrosionBehavior of a Ti-Based Bulk Metallic Glass and Its Crystalline Alloys”(MATERIALS TRANSACTIONS, Vol. 48 (2007), No. 7 pp. 1855-1858) and F. X.Qin, X. M. Wang and A. Inoue “Effect of annealing on microstructure andmechanical property of a Ti—Zr—Cu—Pd bulk metallic glass”(Intermetallics, Volume 15, Issue 10, October 2007, Pages 1337-1342).Recent research works concentrate on metallic glasses based on titaniumand zirconium, such as Zr₅₅Al₁₀Ni₅Cu₃₀,Zr_(100-x-y)(Cu_(z)Ag_(1-z))_(y)Al_(x) (wherein x=7-9 at. %, y=42-50 at.% and z=0.75-0.875 at. %), Zr₅₃Co_(18.5)Al_(23.5)Ag₅,Zr₆₀Nb₅Cu₂₀Fe₅Al₁₀, Zr₆₀Ti₆Cu₁₉Fe₅Al₁₀, Zr₆₀Nb₅Cu_(22.5)Pd₅Al_(7.5), aswell as metallic glasses based on magnesium and zinc, i.e. Mg₆₆Zn₃₀Ca₄ iMg₇₀Zn₂₅Ca₅ oraz Ti_(43.3)Zr_(21.7)Ni_(7.5)Be_(27.5),Ti₄₅Zr_(50-x)Pd_(x)Si₅ (wherein x=35, 40, 45 at. %). Research resultsshow that only metallic glasses of the type Ti₄₅Zr₃₈Ni₁₇ have apotential of use as biomaterials (H. Lefaix, P. Vermaut, S. Zanna, A.Galtayries, F. Prima, R. Portier, “Structural and Functional(Superficial), Biocompability of New Amorphous/Quasicrystalline Ti-BaseComposites”, Tenth Annual Conference Yucomat 2008, PL.S.III.2, p. 36, H.Lefaix, A. Asselin, P. Vermaut, Sautier, A. Berdal, R. Portier, F.Prima, “On the biocompatibility of a novel Ti-based amorphous composite:structural characterization and in-vitro osteoblasts response”, J MaterSci: Mater. Med. 19 (2008) pp. 1861-1869).

Introducing niobium to metallic alloys based on titanium improved theircorrosion resistance in different electrolytes. Ti₆₄Zr₅Fe₆Si₁₇Mo₆Nb₂ andTi₇₀Zr₆Fe₇Si₁₇ metallic glasses are compared by Chunxiang Cui, Ling Bai,Qingzhou Wang, Shaojing Bu and Yumin Qi in “Fabrication of Ti-basedamorphous composite and biocompatibility research” (Journal of WuhanUniversity of Technology—Materials Science Edition, 6 Feb. 2010). Theproperties of metallic glass (Ti₄₀Zr₁₀Cu₃₆Pd₁₄)_(100-x)Nb_(x) (x=1, 3, 5at. %) containing nanoparticles are described by is F. X. Qin, X. M.Wang, G. Q. Xie and A. Inoue “Distinct plastic strain of Ni-freeTi—Zr—Cu—Pd—Nb bulk metallic glasses with potential for biomedicalapplications” (Intermetallics Volume 16, Issue 8, August 2008, Pages1026-1030).

The enhanced corrosion resistance in different electrolytes and goodbiocompatibility have also been reported in a few of other systems withthe addition of niobium, including Zr₅₉Cu₂₀Al₁₀Ni₈Nb₃,(Cu₆₀Zr₃₀Ti₁₀)₉₅Nb₅, Zr₅₅Al_(20-x)Co₂₅Nb_(x) (x=0 to 5 at. %) and(Zr₆₀Nb₅)Cu_(17.5)Ni₁₀Al_(7.5). Also, the addition of niobium canenhanced the stability of the quasicrystalline phase in some Zr-basedalloy compositions, i.e., (Zr₆₅Al_(7.5)Cu_(27.5))₉₅Nb₅ andZr₅₈Al₉Ni₉Cu₁₄Nb₁₀. However, these metallic glasses were still notappropriate for biomedical applications, due to low hardness and lowwear resistance (Jeong-Jung Oak, Akihisa Inoue, “Formation, mechanicalproperties and corrosion resistance of Ti—Pd base glassy alloys”,Journal of Non-Crystalline Solids, vol. 354, year 2008, pp. 1828-1832,Yu-Lai Gao, Jun Shen, Jian-Fei Sun, Gang Wang, Da-Wei Xing, Heng-Ze Xianand Bi-De Zhou, “Crystallization behavior of ZrAlNiCu bulk metallicglass with wide supercooled liquid region”, Materials Letters, vol. 57,year 2003, pp. 1894-1898).

The object of the present invention is to provide a new titanium-basedmetallic alloy with a good biocompatibility.

SUMMARY

A metallic alloy according to the invention comprises Ti, Zr, Nb andcontains an amorphous phase and a quasicrystalline phase and isrepresented by the formula:

Ti_(a)Zr_(b)Nb_(c)M_(d)I_(e),

wherein:

-   -   M represents an element selected from a group consisting of Ni,        Co, Fe, Mn,    -   I represents impurities,    -   coefficients a, b, c, d, e represent atomic %, and are equal to:        40≦a≦55, 5≦b≦30, 5≦c≦25, 5≦d≦30, e≦1.

The quasicrystalline phase can be formed by icoshedral crystals,preferably having size ranging from a few nanometers to 100 micrometers.

The quasicrystalline phase can form from 1% to 80% volumetric fractionof the alloy.

The alloy can be formed by a method of the group containing meltspinning, rapid cooling by squeezing, thermal sputtering—cooling from agaseous phase, ion sputtering techniques.

The object of the invention is also use of the alloy according to theinvention for manufacturing a product intended as an implant for humanor animal body.

The invention also relates to an implant for implantation in the humanor animal body comprising the alloy according to the invention.

BRIEF DESCRIPTION OF THE FIGURES

The object of the invention is shown by means of exemplary embodimentson a drawing, in which:

FIG. 1 shows the structure of a metallic alloy according to theinvention, analyzed by X-ray diffraction (XRD)

FIGS. 2-9 show plots of current density for different alloys accordingto the invention.

FIG. 10 shows a plot of current density for Ti—Zr—Ni alloy.

DETAILED DESCRIPTION OF THE INVENTION

A metallic alloy according to the invention was obtained on the basis ofTi—Zr—Ni and Ti—Zr—Co alloys, by partial substitution of Zr by Nb andsubstitution of Ni by Fe and Mn.

The alloy according to the invention contains an amorphous phase and aquasicrystalline phase and is represented by the following formula:

Ti_(a)Zr_(b)Nb_(c)M_(d)I_(e)

wherein:

-   -   M represents an element selected from a group consisting of Ni,        Co, Fe, Mn,    -   I represents impurities,    -   coefficients a, b, c, d, e represent atomic %, and are equal to:        40≦a≦55, 5≦b≦30, 5≦c≦25, 5≦d≦30, e≦1.

The amorphous phase provides good corrosion resistance and thequasictysalline phase provides high hardness of the alloy.

Preparing alloys comprising an amorphous phase and quasicrystallinephase, comprising Ni, Co, Fe, Mn, depends on various factors, such asthe electron structure of the elements. For alloys according to theinvention, there are maintained appropriate concentrations of metals ofgroups 4 and 5 (i.e. Ti, Zr, Nb) and groups from 7 to 10 (i.e. Ni, Co,Fe and Mn). The used elements Ni, Co, Fe i Mn are easily accessible andaffordable. Optionally, Ni could be replaced by Pd and Pt, Co by Rh andIr, Fe by Ru and Os, Mn by Tc and Re, but these elements are not common(Tc is not present in the Earth soil) and are expensive. Cu has not beenused due to low corrosion resistance.

The structure of the layers as analyzed by X-ray diffraction indicatedthe formation of icoshedral quasicrystalline phase, as shown in FIG. 1.The quasicrystalline phase, i.e. a form of a solid body, in which atomsare aligned in a seemingly regular, but a nonperiodic structure, whichmakes it impossible to distinguish their elementary cells, has beenformed by quasicrystals having sizes from a few nanometers to about 100micrometers, embedded in an amorphous matrix. The volume fraction of theicoshedral quasicrystalline phase in the metallic glass is dependent onthe alloy composition and can be adjusted in order to comply with thedesired properties, ranging from 1 to 80%. The volume fraction of theicoshedral quasicrystalline phase can be controlled by the alloycomposition and the speed of cooling (which can be adjusted e.g. bychanging the speed of rotation in the melt spinning method).

The alloy according to the invention shows excellent corrosionresistance, and therefore is very suitable for use in medicine as partof implants.

The corrosion properties of the alloy according to the invention havebeen investigated in simulated physiological solution at 37° C. (aeratedHanks' balanced salt solution; 8 NaCl, 0.4 KCl, 0.35 NaHCO₃, 0.25NaH₂PO₄×H₂O, 0.06 Na₂HPO₄×H₂O, 0.19 CaCl₂×2H₂O, 0.19 MgCl₂,0.06MgSO₄×7H₂O, 1 glukoza, w g/l) by means of potentio-dynamic test. Thelayers exhibit a low value of the corrosion current density in the range(1-5)*10⁻⁶ A/cm² i and passivation current density In the range(6-7)^(*)10⁻⁵ A/cm². The corrosion current density has been measured bya Tofel extrapolation method, wherein exemplary plots for variousembodiments of the alloys are presented in FIGS. 2-9.

The alloy according to the invention exhibits high wear resistance andincreased hardness, as indicated by the measurements below:

Alloy Vickers microhardness Ti₄₅Zr₂₈Nb₁₀Ni₁₇ 414 Ti₅₀Zr₁₅Nb₁₅Co₂₀ 406Ti₆₅Zr₁₀Nb₁₀Fe₁₅ 525 Ti₅₀Zr₁₀Nb₁₅Mn₂₅ 495 Ti₄₅Zr₃₈Ni₁₇ 396 Ti₆₅Zr₁₀Fe₂₅375 Ti₅₀Zr₂₅Mn₂₅ 344

As indicated by the measurements in the table above, partial replacementof Fe and Mn by Nb increases the hardness of the alloys by 30% for Fealloys and by 40% for Mn alloys.

In addition, the alloys according to the invention, as shown in FIGS.3-9, are characterized by a wide range of passivation, i.e. from 1.0 to1.5V, in contrast to an alloy which does not contain niobium, as shownin FIG. 10, for which the range of passivation equals only 0.2 V. Thisproperty is particularly important in relation to corrosion, i.e. thentitanium is in contact with other metallic materials.

The partial replacement of Zr by Nb provides a extension of thepassivation region to a large value of the potential up to about 1.5V.

The alloy according to the invention can be manufactured by the methodsknown for metallic glasses, for example by the melt spinning methoddescrived by Cahn [W. Cahn, Physical Metallurgy, Third edition, ElsevierScience Publishers B.V., 1983] and Liebermann [Liebermann H. and GrahamC., Production Of Amorphous Alloy Ribbons And Effects Of ApparatusParameters On Ribbon Dimensions, IEEE Transactions on Magnetics, VolMag-12, No 6, 1976, pp. 921-923], by rapid cooling by squeezing asdescribed in the Polish patent application PL384142 or by melt isspinning according to the Polish patent application PL378301, as well asby thermal sputtering—cooling from a gaseous phase or by ion sputteringtechniques.

1. A metallic alloy comprising Ti, Zr, Nb, characterized In that itcontains an amorphous phase and a quasicrystalline phase and isrepresented by the formula:Ti_(a)Zr_(b)Nb_(c)M_(d)I_(e), wherein: M represents an element selectedfrom a group consisting of Ni, Co, Fe, Mn, I represents impurities,coefficients a, b, c, d, e represent atomic %, and are equal to:40≦a≦55, 5≦b≦30, 5≦c≦25, 5≦d≦30, e≦1.
 2. The metallic alloy according toclaim 1, characterized in that the quasicrystalline phase is formed byicoshedral crystals.
 3. The metallic alloy according to claim 1,characterized in that the quasicrystalline phase is formed byquasicrystals having size ranging from a few nanometers to 100micrometers.
 4. The metallic alloy according to claim 1, characterizedin that the quasicrystalline phase forms from 1% to 80% volumetricfraction of the alloy.
 5. The metallic alloy according to claim 1,characterized in that it is formed by a method of the group containingmelt spinning, rapid cooling by squeezing, thermal sputtering—coolingfrom a gaseous phase, ion sputtering techniques.
 6. Use of the alloyaccording to claim 1 for manufacturing a product intended as an implantfor human or animal body.
 7. An implant for implantation in the human oranimal body comprising an alloy according to claim 1.